This family members can be desribed as follows: they are the smooth prime divisors of bidegree (1,2) in \(\mathbb {P}^2\times \mathbb {P}^2\) . Let \(\mathbb {P}^2\times \mathbb {P}^2=\lbrace [x,y,z]\times [u,v,w]\rbrace \) , then according to [1]} Lemma A.7.10, we have that every member in this family belongs to one of the following three cases:
